[Dev-luatex] Traversing node list

[Hartmut Henkel]

On Thu, 30 Oct 2008, Khaled Hosny wrote:

> I'm wondering why, in the following code, the first \hbox{} is not seen
> by the lua function while the second one is seen i.e. \hbox{} at
> paragraph beginning isn't seen.
>
> \directlua0{
> local function traverse(h)
>   for n in node.traverse (h)
>     do texio.write_nl('node id='..node.type(n.id))
>     if n.id == node.id('hlist') then
>       traverse(n.list)
>     end
>   end
> end
> callback.register('pre_linebreak_filter',
>   function(h)
>     traverse(h)
>     return true
>   end
> )
> }
>
> \hbox{Not seen}

that's just a \hbox{} within the page's \vbox{}, it's not starting a
paragraph. A \hbox{} at the beginning of a new paragraph you would get
e. g., by \leavevmode\hbox{Seen}.

>
> Hello \hbox{seen}
> \bye

Regards, Hartmut